No miss fire roller cam for automotive distributor assemblies

ABSTRACT

An improved multi-lobed cam for use in automotive distributors and the like is shown. The cam is formed by arranging a plurality of rollers in a circle with the rollers providing the cam lobes and spaces therebetween the cam flats so that wobble of the cam will have no effect on the cam follower when it is in the spaces thus preventing the points from opening at the wrong time and causing a miss-fire.

United States Patent 1191 Rhinesmith Aug. 28, 1973 [54] 0 M ss F E R LL A R 2,740,853 4/1956 Hartman, Jr... 200/30 A AUTOMOTIVE DISTRIBUTOR ASSEMBLIES 2,759,371 8/ 1956 Whlte 74/568 2,990,459 6/1961 Stambro et a1. 200/30 A [76] Inventor: Warren John Rhinesmlth, Unlon 3,175,423 3/1965 Valley Rd., Box 225, West Milford, 3,197,580 7/1965 NJ. 3,339,535 9/1967 3,575,579 4/1971 McGannon 200/30 A X [22] Flledz Dec. 7, 1971 [2]] Appl. No.: 171,182 Primary Examiner-J. R. Scott 52 U.S. c1. 200/19 R, 200/30 R 1 ABSTRACT 51 1111. C1. 110111 3/42 An Improved mum-lobed cam for use euwmellve 58 Field of Search 200/19 R, 19 DR, distributors and the like is ehewn- The eam is formed 200/19 DC, 19 A, 30 R, 30 A; 74/568 R, 567 by arranging a plurality of rollers in avcircle with the rollers providing the cam lobes and spacestherebe- 56] References Cited tween the cam flats so that wobble of the cam will have UNITED STATES PATENTS no effect on the cam follower when it is in the spaces 1 494 597 5/1924 E 200/19 DR thus preventing the points from opening at the wrong vans 1,997,288 4/1935 Anderson 200/30 A and causmg a 2,348,896 5/1944 Gibson et a1 200/30 A 4 Claims, 2 Drawing Figures 4 e t s b spark plugs are caused to fire in response to the open ing of a set of distributor contacts or points as they are commonly known. The points are opened by a follower which rides on a cam having a number of lobes equal to the number of cylinders in the engine. The distribor cam is coupled to the cam shaft of the engine to mychronize firing with valve operation. Such ignition systems are well known in the prior art. For example, see U.S. Pat. No. 1,997,288, granted to H. F. Anderson on Apr. 9, 1935. Typical cam operation to open and close distributor points is shown in U.S. Pat. No. 2,740,853 granted to F. W. Hartman, Jr. on Apr. 3, I956.

In most engines the distributor shaft is coupled to the high pressure oil pump used to supply lubricating oil to the engine. Forces developed in the oil pump and the unequal forces from the cam shaft which drives the oil pump and distributor are transmitted to the distributor shaft to which the cam is affixed causing the shaft bushing to wear which causes the cam to wobble. Thus wobble, which can become particularly pronounced at high speeds, often causes the cam flat to push against the cam follower causing the points to open and theengine to miss-fire. Even if the points do not open long enough to supply sufficient spark to fire the cylinder they will partially discharge the charge being built to in the coil or magneto and there will notbe enough time to store a proper amount of energy before reaching the proper firing point at a cam lobe. In that case, the cylinder will not fire properly reducing the power and efficiency of the engine. Thus, it is evident that there is a need for a type of cam which prevents the points from opening except when at a cam lobe.

SUMMARY OF THE INVENTION The cam of the present invention prevents improper opening of the points by using rollers as the cam lobes and spaces therebetween as the cam flats. The rollers are arranged in a circle around the distributor shaft and held between two annular lips on a member mounted to the shaft for rotation therewith. Each roller is held between the two lips by a pin inserted through a hole in its center and is free to rotate about the pin. As the member with the rollers mounted thereto is rotated with the distributor shaft, the cam follower will be pushed outward by the rollers to open the points. The number of rollers is equal to the number of cylinders and means are provided to adjust the position of the cam relative to the distributor shaft so that the rollers will open the points at the proper firing time. However, when between rollers, in the space corresponding to the flat on a conventional cam, there is no surface present to push against the cam follower and wobble of the shaft cannot possible open the points.

In addition, the cam of the present invention provides sharper opening and closing of the points, and thereby causes the points to last longer due to reduced pitting. The system is also easy to adjust, not requiring dwell measurement and adjustments to be made since the spaces between the rollers provide a constant dwell at all times.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of the preferred embodiment of the cam of the present invention.

FIG. 2 is a cross-sectional elevation view of the same embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The cam assembly as shown on FIGS. 1 and 2 is designated generally as 11 and is comprised of an annular body member 5 with upper and lower lips 15 and 17 a plurality of rollers 4, and a plurality of pins 3 holding rollers 4 between lips 15 and I7. Rollers 4 have an internal diameter which is slightly larger than the diameter of pins 3 so that the rollers are free to rotate on the pins. In this way, when the rollers contact the cam follower they will rotate as the follower rides up on them providing smoother action and reducing wear on the follower. Pins 3 are held securely in lips 15 and 17 by press fitting or the like.

The cam structure 11 is mounted to one end of a member 2 which has on its other end a plate 1 containing slots 7 into which centrifugal advance pads may be inserted in a well known manner. Member 2 is cylindrically shaped with a central hole 8. Th'e distributor shaft will be inserted into hole 8 and member 2 securely fastened to the shaft for rotation therewith in a conventional fashion. The cam apparatus 11 is secured to member 2 by set screws 6 and will thus also rotate with the distributor shaft. Timing may be adjusted by loosening set screws 6 and rotating apparatus 11 until rollers 4 are properly positioned and then tightening the set screws 6 to maintain the setting. The top portion of member 5 contains a slot 9.to receive a distributor rotor in a well known manner.

Thus, an improved cam for an automobile distributor or the like has been shown in which rollers are used as cam lobes and the spaces therebetween as the cam flats thereby preventing opening of the points at the wrong time. Although a specific embodiment has been shown and described, it will be obvious to those skilled in the art that various modifications may be made without departing from the spirit of the invention which is intended to be limited solely by the appended claims.

I claim:

1. A distributor cam apparatus comprising:

a. an annular member having a center hole for mounting to the distributor shaft said member having upper and lower lips projecting therefrom;

b. a plurality of annular rollers;

c. an equal plurality of pins having a diameter less than the inner diameter of said rollers and each inserted through the center of one of said rollers and held between said upper and lower lips in a circular, equally spaced arrangement.

2. The invention according to claim 1 and further including a second annular member having a center hole for mounting said second annular member onto said distributor shaft, and having a portion for insertion into the center hole of said first annular member, and means to secure said first annular member to second annular member for rotation therewith.

3. The invention according to claim 2 wherein said means to secure comprises at least one set screw whereby said second annular member can be pennanently affixed to said distributor shaft and the timing in said distributor adjusted by moving said first annular member relative to said second member.

4. The invention according to claim 3 and further including a plate secured to said second annular member said plate containing slots to receive centrifugal advance mechanisms. 

1. A distributor cam apparatus comprising: a. an annular member having a center hole for mounting to the distributor shaft said member having upper and lower lips projecting therefrom; b. a plurality of annular rollers; c. an equal plurality of pins having a diameter less than the inner diameter of said rollers and each inserted through the center of one of said rollers and held between said upper and lower lips in a circular, equally spaced arrangement.
 2. The invention according to claim 1 and further including a second annular member having a center hole for mounting said second annular member onto said distributor shaft, and having a portion for insertion into the center hole of said first annular member, and means to secure said first annular member to second annular member for rotation therewith.
 3. The invention according to claim 2 wherein said means to secure comprises at least one set screw whereby said second annular member can be permanently affixed to said distributor shaft and the timing in said distributor adjusted by moving said first annular member relative to said second member.
 4. The invention according to claim 3 and further including a plate secured to said second annular member said plate containing slots to receive centrifugal advance mechanisms. 